Benavides Jose
USA – University of California, Riverside
Stellar metallicity and assembly history of ultra-diffuse galaxies in TNG50
We study the observational properties of a sample of simulated ultra-diffuse galaxies (UDGs) in high density environments from the TNG50 simulation. These satellite UDGs have been found to form in high-spin dwarf-mass halos with overall little impact from tidal stripping or gravitational heating effects, and may be used to benchmark the predictions for the scenario where UDGs are linked to high-spin halos. On average, we find that UDGs are 70% poorer in [Fe/H] than the population of non-UDGs at a fixed stellar mass and present relatively small scatter ~0.1 dex. At fixed metallicity, simulated UDGs are predicted to be more alpha-enhanced, as traced by [Mg/Fe], than the non-UDG sample. In both cases, [Fe/H] and [Mg/Fe], the simulated UDGs are unable to reproduce the large spread reported in observational samples. Simulated UDGs that have experienced significant mass loss (more than 50% of the stars) tend to be more metal rich than non-stripped UDGs of similar mass, albeit this effect is small and unable to reproduce the observed scatter. Our simulations predict a very strong negative gradient in metallicity with radius, which is significantly steeper than the ones reported in UDGs formed by internal mechanisms like feedback. This hints to the possibility of using metallicity profiles to indicate formation path for these objects. In terms of star formation histories, once we separate the population of quenched and star-forming satellites, we find good agreements between UDG and non-UDG dwarfs. However, we find that on median UDGs tend to quench more quickly than their non-UDG counterparts after infall by about ~1 Gyr. We interpret this as the result of a more efficient ram-pressure stripping due to the smaller gravitational restoring force provided by the extended baryonic distribution in UDGs.